How do I troubleshoot inoperative door locks? on 1998 GMC Suburban 1500

The automatic door locks just quit working, without warning, on all four doors.

Asked by for the 1998 GMC Suburban 1500
Autozone have some popular workshop manuals for free on line once you register (for free) on their website There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate